U.S. Pat. No. 6,354,444 describes an asymmetric membrane comprising a tubular polymeric film supported on a tubular braid. The braid is flexible yet strong enough to withstand flexing and stretching when the membrane is used for microfiltration (MF) or ultrafiltration (UF). The braid is prefabricated according to specified physical parameters such that the braid has a wall thickness in the range of 0.2 mm to 1.0 mm and limited air permeability. The tubular polymeric film has a thickness of less than 0.2 mm and is formed by casting a dope on the braid while the braid is fed through a coating nozzle. Although the braid is self-supporting, the coating nozzle includes a rounding orifice to ensure that the braid is completely round before the dope is coated over it. The tubular polymeric film is supported on the outer circumferential surface of the braid without the braid being embedded in the tubular polymeric film. The coated braid travels through a coagulation tank in which the dope is converted into the polymeric film.
International Publication Number WO 2010/148517 describes various methods of making non-braided textile-reinforced hollow fiber membranes. Some of the methods provide a reinforcing structure that includes filaments extending around the circumference of the membrane but without the filaments being part of a braided or woven structure. Some of the reinforcing structures also include longitudinal filaments. The reinforcing structures are embedded in the membrane wall. The membranes have a ratio of inside-to-outside diameters of 0.5 or more.